Electric fuse



1961 T. A. BURDESHAW ELECTRIC FUSE 2 Sheets-Sheet 1 Filed April 22, 1959 INVENTOR. THOMAS A. BURDESHAW ATTORNEY Jan. 31, 1961 T. A. BURDESHAW ELECTRIC FUSE 2 Sheets-Sheet 2 Filed April 22, 1959 FIG. 5

FIG.4

INVENTOR. THOMAS A. BURDESHAW ATTORNEY Erncrnrc ruse Thomas A. Eurdeshaw, Hampton, Ga, assignor to Southern States Equipment Corporation, a corporation of Georgia Filed Apr. 22, 1959, Ser. No. 3%,073

Claims. (Cl. 209-114) This invention relates to electric fuses and more particularly to an improved toggle type latching means for high voltage electric fuses.

It is customary to provide electric fuses and cutouts with a conducting element pivotally mounted adjacent one end of the fuse tube and to secure it to the outwardly extending end of the fusible element disposed within the fuse tube 50 as normally to maintain the conducting element in its normal closed circuit position relative to the fuse tube. Upon rupture of the fusible element, a force due to spring biasing means, contact pressures and to the weight of the fuseholder exerts a turning moment which causes the conducting element to move out of its normal position relative to the fuse tube. In such a construction the weight of the fuseholder and parts associated therewith, together with the spring and contact bias, tend to rotate the, conducting element relative to the fuse tube and thereby impose a tension stress on the fusible element. In high voltage power fuses where the fuse tube is quite long the weight of the tube and the force exerted by the biasing elements constitute a substantial strain on the fusible element.

In order to relieve the fusible element of such strain it has been the practice to mount a link ejector on a pivot provided on the conducting element and to provide the link ejector with a latching surface arranged to cooperate with a corresponding latching surface afiixed to the fuse tube or to a part associated therewith. In this manner the ejector element is required to take a substantial portion of the strain due to the weight of the fuseholder and to the various biasing forces, the ejector being maintained in its latching position by the fuse link itself.

Such an arrangement wherein the ejector performs the stress relieving function as above described, it sometimes happens that upon rupture of the fuse link the fuse fails to drop out due to a high friction relation between the latching surfaces of the ejector element and of the latch mounted on the fuse tube.

A principal object of this invention is to provide low friction latching means for electric power fuses and cutouts which means is capable of dependable operation under all conceivable conditions.

Another object of this invention is to provide a toggle latch for electric fuses and cutouts which is characterized by low friction and which is adapted to function not only to relieve the stress normally imposed on the fusible element but which also is adapted to perform as an auxiliary link ejector whereby positive and sure link ejection is assured together with reliable dropout action.

The invention in one form as applied to a power fuse or cutout having a conducting element pivotally mounted to one end of the fuse tube comprises a toggle linkage interconnected between the fuse tube and the conducting element and normally arranged to ocupy a position approximating dead center so that the conducting element is maintained in its normal position relative to the fuse tube by the action of the toggle means. As an aid to insuring positive operation of the toggle linkage during fault ice conditions, a suitable biasing element ordinarily is provided in accordance with the invention which tends to impart movement to the toggle thereby to aid in accommodating relative movement of the conducting element relative to the fuse tube. According to another feature of the invention, the toggle element is maintained in its normal position under normal conditions by the fuse link itself, the outwardly extending end of the fuse link being normally interconnected with the conducting element to form an electric connection therebetween.

The invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings in which Fig. 1 is a side view of a conventional power fuse to which the invention is applicable; Fig. 2 is a bottom view of the lower end of a power fuse to which the invention is applied; Fig. 3 is a view partially in section of the structure shown in Fig. 2 and which is taken along the line 3-3 indicated in Fig. 2; Fig. 4 is a view taken along the line 44 as indicated in Fig. 2 and showing the parts in their normal positions; Fig. 5 is a view similar to Fig. 4 but which shows the parts in the positions which they occupy immediately following rupture of the fusible element at the beginning of a circuit interrupting operation; Fig. 6 is a view similar to Figs. 4 and 5 and which shows the parts in the positions which they occupy after the fuse tube has moved to its lowermost position but before the assembly has dropped out; and in which Fig. 7 is a view similar to Figs. 4, 5 and 6 but which shows the parts in the positions which they occupy when the fuse has dropped out.

With reference to Fig. l, the numeral 1 designates a metallic base such as a channel element on which the insulator stacks 2 and 3 are secured in known manner by means of bolts 5 and 6. Secured to the right-hand end of insulator stack 2 is a terminal assembly 7 which is provided with a terminal pad 8 and a sleet hood 9 pivoted at It? to the right-hand end of the terminal assembly 7.

Afiixed to the right-hand end of insulator stack 3 is a terminal assembly 11 which is provided with a terminal pad 12 and with a pair of spaced jaws 13. A conventional snubber is designated at 13A in Fig. 2.

As is Well known, the fuseholder 14 forms a current responsive connection between terminal assemblies 7 and fl and the circuit controlled by the fuse is connected to terminal pads 8 and 12.

Fuseholder 14 comprises a fuse tube 15 of insulating material to which is affixed at the lower end thereof a metallic terminal element 16 securely afiixed as by pin MA as best shown in Fig. 3 to the fuse tube 15. Pivotally mounted to terminal element 16 at pin 17, best shown in Fig. 3, is a conducting element 18. Conducting element 18 is provided with a pair of spaced trunnions 19 which ride in the jaws 13 formed in the terminal assembly 11. Conducting element 18, as is well known, is held in its normal position, such as is indicated in Fig. 4 for example, by the outwardly extending end 20 of the fusible element disposed within the fuse tube 15. The connection between outward y extending end 20 of the fusible element and the conducting element 18 is in the form of suitable securing clamp 21. A biasing spring 22, best shown in Fig. 3, tends to impart clockwise rotation to conducting element 18 about the pin 17. This biasing force of spring 22 together with the weight of the fuseholder 14 and of the contact brush (not shown) which establishes an electric connection between terminal element 11 and conducting element 18 all tend to impose a tension stress on extension 20 and on the fusible element disposed within the fuse tube 1.5.

The upper end of the fuseholder 14 is interconnected with the terminal structure 7 by means of a terminal element 24 which is secured by a pin 25 or other suitable means to the insulating fuse tube 15. The left-hand extremity of the terminal element 24 is provided with a contacting surface which engages a resilient contact mounted underneath the sleet hood 9 and not shown in the drawings. Furthermore, as is well known, the upper portion of the left-hand end of the terminal element 2 2- is provided with a latch which engages a corresponding latching surface formed within the sleet hood 9. Sleet hood 9 is provided with suitable biasing means (not shown) which tends to rotate the sleet hood in a clockwise direction about the pivot lit for a limited distance until a stop (not shown) is encountered.

From the description thus far it will be understood that when the conducting element 18 at the lower end of the fuse tube is released upon rupture of the fusible element within the tube, the fuseholder 14 initially drops downwardly and unlaches the left-hand end of terminal element 24 from the latch within the sleet hood 9 and thereafter the entire assembly associated with fuseholder 14 swings in a clockwise direction about the trunnions 19 until the parts occupy the position generally indicated in Fig. 7, all in conventional manner.

A suitable opening 26 is formed in the terminal element Z4 and is for the purpose of enabling an operator to manipulate the fuse by a hookstick or otherwise and an opening 2-3 is formed integrally with the conducting element 18 for a similar purpose.

Where conventional latching ejectors are provided, the ejector is pivotally mounted on a conducting element such as conducting element 18 and the ejector latchingly engages a part mounted on the lower end of the fuse tube '15. The friction relationship between the latching surfaces in such conventional structures may be substantial and may prevent the cutout or fuse from dropping out. According to this invention positive and quick dropout action is assured even in high voltage power fuses in which the weight is considerable and in which the biasing forces are substantial.

Toward this purpose the conducting element 18 is maintained in its normal position relative to the fuse tube 15 by a low friction toggle linkage which, in its normal position approximating dead center, acts to hold the conducting element 18 in its normal position and which is movable to an operated position upon rupture of the fusible element disposed within the fuse tube 15 to allow the conducting element lit to move out of its normal position relative to fuse tube 15 and thereby to allow the fuseholder 14 to drop out.

As is best shown in Figs. 2, 3, and 4, this linkage comprises a tension link 27 which is pivoted y pin 23 to the conducting element 13 and which is interconnected by knee pin 29 to the compression link 30 pivoted by pin 31 to the downwardly extending portion 32 of the terminal element 16. As is well understood, the ends of links 27 and 30 which are connected by knee pin 29 constitute the knee of the toggle. As is best shown in Figs. 2 and 3, a biasing spring 33 is disposed about the pin 31 and one end thereof designated 33A engages the downwardly extending part 32 of terminal element 16 while the other end thereof designated 33B engages the center ribatlA of the compression link 39. The toggle biasing spring 33 is arranged to exert a clockwise turning moment on the compression link 34} tending to rotate that link in a clockwise direction about the pin 31. it will be understood that the toggle spring 33 is a relatively weak spring whereas the biasing spring 22 is fairly heavy in construction.

Thus with the parts in their normal positions as indicated in Pig. 4, the weight of the fuseholder 14 the bias of spring 22 and the bias of the contacts (not shown) interconnecting the terminal assembly 11 and the conducting element 18 all tend to impose a tension stress on the fuse link and the extension 20. Since the pin 28 in the normal position indicated in Fig. 4 is substantially in line with the pin 29 and the pin 31 it will be obvious that a force normally is exerted via the toggle elements 27 and 30 which tends to maintain the conducting element 18 in its normal position relative to fuse tube 3.5 and that the only stress on the fuse link and on the extension 20 is that required to hold the toggle elements 27 and 30 in their normal positions as indicated in Fig. 4. This tension stress is obviously of a low order of magnitude and is not likely to damage the fusible element or to interfere with its operation in any way, and furthermore, since the pivots 2.8, 29, and 31 are of low friction construction there is virtually no possibility that the fuse tube will fail to drop out when the fuse link ruptures during fault conditions. In this manner positive and dependable operation is assured.

The parts in Fig. 5 as already explained are shown in the positions which they occupy immediately following rupture of the fusible element disposed within the fuse tube 15. it will be observed that the toggle in Fig. 5 has moved out of its normal position and it will be understood that this movement is aided by the action of the 0 toggle spring 33. In Fig. 5, however, the conducting element 18 has not yet moved relative to the fuse tube 15 and parts associated therewith.

After the toggle is moved to its fully released position of course the conducting element 18 is free to move under the weight of the fuse tube assembly 14 and the force of biasing spring 22 and of the contact bias to the position shown in Fig. 6, the toggle elements having assumed their extended position as there indicated. Thereafter the entire fuseholder 14 swings clockwise as already explained about the trunnions 19 to the position indicated in Fig. 7 and such dropout action, as already explained, is fully assured due to the low friction construction of the toggle latch comprising the tension link 27 and the compression link 30. Dropout of the fuse- 35 holder is arrested by snubber 13A in conventional manner.

It will be understood that the link pivoted to the terminal element 16 could be the tension element and the link pivoted to the conducting element 13 could be the compression element provided the parts were reoriented in a manner obvious to one skilled in the art.

Furthermore, it will be understood that the toggle could be in its position approximating dead center when the parts would be fully extended in a straight line rather than being generally coincidental as shown in Fig. 4. T 0 this end substantial rearrangement of the parts would be required as will be obvious although it is to be understood that such an arrangement is clearly contemplated as being within the purview of this invention and is intended to be covered in the claims.

While I have shown and described certain embodiments of the invention, I do not wish to be limited thereto and intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric fuse comprising a fuse tube, a fusible element mounted within said tube with one end thereof 0 extending out of one end of said tube, a conducting element pivotally mounted to said one end of said tube, said one end of said fusible element being connected to said conducting element so as normally to form an electric connection therebetween, a toggle linkage interconnected 5 between said one end of said tube and said conducting element and having a normal position approximating dead center and corresponding to the normal position of said conducting element relative to said tube, said one end of said fusible element normally being operably re- 0 lated with said toggle linkage adjacent the knee thereof to hold said linkage in its position approximating dead center, and toggle biasing means for causing said toggle linkage to move out of its position approximating dead center in coordination with the rupture of said fusible 5 element.

2. An electric fuse comprising a fuse tube, a fusible element mounted within said tube with one end thereof extending out of one end of said tube, a conducting element pivotally mounted to said one end of said tube, said conducting element being normally biased for movement out of its normal position relative to said tube and said one end of said fusible element being connected to said conducting element so as normaily to form an electric connection therebetween, and a toggle linkage comprising a tension link and a compression link, said links being pivotally connected together with one of said links pivotally connected with said one end of said fuse tube and with the other of said links pivotally connected with said conducting element, said linkage normally occupying a position approximating dead center in which position said linkage tends to hold said conducting element in its normay position relative to said tube, said fusible element normally being operably related with said toggle linkage so as to hold said linkage in its normal position approximating dead center.

3. An electric fuse comprising a fuse tube, a fusible element mounted Within said tube with one end thereof extending out of one end of said tube, a conducting element pivotally mounted to said one end of said tube, said conducting element being normally biased for movement out of its normal position relative to said tube and said one end of said fusible element being connected to said conducting element so as normally to form an electric connection therebetween, a toggle linkage comprising a tension link and a compression link, said links being pivotally connected together with one of said links pivotally connected with said one end of said fuse tube and with the other of said links pivotally connected with said conducting element, said linkage normally occupying a position approximating dead center in which position said linkage tends to hold said conducting element in its normal position relative to said tube, said fusible element normally being operably related with said toggle linkage so as to hold said linkage in its normal position approximating dead center, and toggle biasing means for causing said toggle linkage to move out of its position approximating dead center in coordination with the rupture of said fusible element.

4. An electric fuse comprising a fuse tube, a fusible element mounted within said tube with one end thereof extending out of one end of said tube, a conducting element pivotally mounted to said one end of said tube, said conducting element being normally biased for movement out of its normal position relative to said tube and said one end of said fusible element being connected to said conducting element so as normally to form an electric connection therebetween, a tension link pivotally mounted on said conducting element, a compression link pivotally mounted on said one end of said fuse tube, and means constituting a pivotal connection between said links to form a toggle linkage interconnecting said one end of said tube and said conducting element, said linkage normally occupying a position approximating a dead center toggle relationship thereby tending to maintain said conducting element in its normal position relative to said tube, said fusible element normally being in engagement with said linkage and being effective normally to maintain said linkage in its position approximating dead center.

5. An electric fuse comprising a fuse tube, a fusible element mounted within said tube with one end thereof extending out of one end of said tube, a conducting element pivotally mounted to said one end of said tube, said conducting element being normally biased for movement out of its normal position relative to said tube and said one end of said fusible element being connected to said conducting element so as normally to form an electric connection therebetween, a tension link pivotally mounted on said conducting element, a compression link pivotally mounted on said one end of said fuse tube, means constituting a pivotal connection between said links to form a toggle linkage interconnecting said one end of said tube and said conducting element, said linkage normally occupying a position approximating a dead center toggle relationship thereby tending to maintain said conducting element in its normal position relative to said tube, said fusible element normally being in engagement with said linkage and being effective normally to maintain said linkage in its position approximating dead center, and a toggle spring arranged to exert a biasing force between said fuse tube and said compression link which tends to move said linkage out of its position approximating dead center.

References Cited in the file of this patent UNITED STATES PATENTS 2,179,749 McCluskey et a1 Nov. 14, 1939 2,400,850 Steinmayer et al. May 21, 1946 2,836,681 Bracey May 27, 1958 2,843,704 Wood July 15, 1958 2,862,080 Yonkers Nov. 25, 1958 

